Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session N07: FOCUS: Advanced SpectroscopyFocus Live
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Sponsoring Units: GPMFC Chair: David Leibrandt, NIST Room: E145-146 |
Thursday, June 4, 2020 10:30AM - 11:00AM Live |
N07.00001: Precision measurement of atomic isotope shift for new physics searches. Invited Speaker: Nitzan Akerman Atomic isotope shift (IS) is the isotope-dependent energy difference in the atomic electron energy levels. These shifts serve an important role in atomic and nuclear physics. Recently, precision spectroscopy of IS was suggested for the search of new forces beyond the standard model. The idea relies on nonlinearity of King plots for narrow optical transitions. To date, the best King plot was measured with precision on the order of 100 Hz and only very few IS were measured at the Hz level. We present a simple scheme to measure the IS with mHz precision. Instead of measuring the absolute transition frequency for each of the isotopes separately, we extract only the shift by measuring the parity oscillations of two isotopes that were prepared in an entangled state. In a recent experiment we demonstrated this method on the quadrupole transition S$_{\mathrm{1/2\thinspace }}$- D$_{\mathrm{5/2}}$ in Sr$^{\mathrm{+}}$ isotopes. The IS shift between $^{\mathrm{86}}$Sr$^{\mathrm{+}}$ and $^{\mathrm{88}}$Sr$^{\mathrm{+}}$ was measured to be 570,264,063.435(5)(8) (statistical)(systematic) Hz. Furthermore, we were able to detect a relative difference of 3.46(23) 10$^{\mathrm{-8}}$ between the orbital g-factors of the electrons in the D$_{\mathrm{5/2}}$ level of the two isotopes. Interestingly, uncorrelated states can be used as well with a penalty of reducing the signal to noise ratio by a factor of two. Thus, making this method applicable to existing setups of trapped ions as well as neutral atoms in optical tweezers. Testing King linearity at the sub-Hz level may be able to improve bounds on new physics and have interesting prospects for testing quantum many-body calculations and the study of nuclear structure. [Preview Abstract] |
Thursday, June 4, 2020 11:00AM - 11:30AM Live |
N07.00002: Ramsey-comb spectroscopy at short wavelengths for fundamental tests Invited Speaker: Kjeld Eikema Spectroscopy of atoms and molecules has become ever more advanced and accurate, especially after the invention of the frequency comb laser. Precision spectroscopy can be used to e.g. test fundamental physics such as bound-state QED, or for determining fundamental constants. We pursue two targets for those purposes, 1S-2S spectroscopy of singly-ionized helium, and a determination of the ionization potential of molecular hydrogen, which require light sources at deep-ultraviolet or shorter wavelengths for excitation from the ground state. Despite demonstrations of e.g. extreme ultraviolet frequency comb generation by nonlinear upconversion, precision spectroscopy remains challenging at such wavelengths. We developed a method, called Ramsey-comb spectroscopy (RCS), that largely overcomes those challenges. It is based on direct excitation with only two amplified and upconverted ultrafast frequency comb laser pulses to generate a form of Ramsey fringes. The frequency comb laser provides the required phase and timing control of the light pulses, while the short pulses enable amplification to high peak power for efficient upconversion of the optical frequencies. By comparing Ramsey signals recorded at two or more inter-pulse delays (spaced at multiples of the comb repetition time), the phase evolution of signal is recorded as a function of time, from which an accurate transition frequency is determined. In the talk I will discuss how this works, and illustrate it with our latest progress on RCS of the X-EF transition in para-hydrogen at 202 nm, and with our recent demonstration of RCS of xenon at 110 nm where we reached the highest spectroscopic accuracy achieved so far with light produced by high-harmonic generation. This experiment was done in preparation of exciting the 1S-2S two-photon (using 32 nm and 790 nm) transition in trapped, singly-ionized helium, which will be discussed too [Preview Abstract] |
Thursday, June 4, 2020 11:30AM - 11:42AM Live |
N07.00003: Towards Sub-Hertz Resolution Rotational Spectroscopy of a Single Molecular Ion Alejandra Collopy, Tara Fortier, Scott Diddams, Dietrich Leibfried, David Leibrandt, Chin-Wen Chou We perform precision rotational spectroscopy and coherent quantum state manipulation [1] on a CaH$^{+}$ molecular ion. State preparation and readout are implemented through quantum logic operations on a co-trapped Ca$^{+}$ atomic ion. We coherently drive Raman transitions within or between rotational manifolds of the molecular ion with a 1051 nm fiber laser or a Ti:Sapph laser frequency comb, respectively. Completion of a certain molecular transition is heralded by a detectable state change of the Ca$^{+}$ ion. We currently achieve sub-100 Hz resolution of THz rotational transitions and anticipate achieving sub-Hz resolution by increasing the coherence of the frequency comb. A limitation of the accuracy of our rotational transition frequency measurements is the effect of the trap rf electric field. Such an electric field is unavoidable due to trap inhomogeneities and becomes more exaggerated for larger ion crystals. As a consequence of this rf field, we observe mixing of closely spaced (a few hundred Hz) states within rotational manifolds, as well as frequency shifts of rotational transitions. These shifts in turn allow us to derive a value of the molecular electric dipole moment. [1] C.-W. Chou et al. arXiv:1911.12808 (2019) [Preview Abstract] |
Thursday, June 4, 2020 11:42AM - 11:54AM Live |
N07.00004: Online portal for high-precision atomic physics data and computation Marianna Safronova, P. Barakhshan, R. Eigenmann, C. Cheung, S.G Porsev, M.G. Kozlov, A. Marrs In a number of present applications, ranging from studies of fundamental interactions to development of future technologies, accurate atomic theory is indispensable to the design and interpretation of experiments, with direct experimental measurement of relevant parameters being impossible or infeasible. The goal of our project is to create an online portal for high-precision atomic physics data and computation that will provide a variety of services to address the needs of the widest possible community of users. The first version of the portal, demonstrated here, provides a wide range of transition matrix elements, static, and dynamic polarizabilities for a number of atoms and ions, including Li, Be$^+$, Na, Mg$^+$, K, Ca$^+$, Rb, Sr$^+$, Sr, Ba$^+$, Fr, Ra$^+$, and others. The data are calculated using a high-precision state-of-the-art coupled-cluster (CC) method or a hybrid method that combines configuration interaction and CC. All values include estimated uncertainties. Experimental values are also included with references where high-precision data are available. We seek community input to improve the portal and guide the next stages of the project which will include more complicated systems and capabilities to compute atomic properties on demand via portal. [Preview Abstract] |
Thursday, June 4, 2020 11:54AM - 12:06PM |
N07.00005: Hyperfine and fine structure measurements of the 2 $^{\mathrm{3}}$S and 2 $^{\mathrm{3}}$P states of $^{\mathrm{7}}$Li$^{\mathrm{+}}$ Hua Guan, Shaolong Chen, Shiyong Liang, Wei Sun, Pengpeng Zhou, Xiaoqiu Qi, Yao Huang, Peipei Zhang, Zhenxiang Zhong, Zongchao Yan, Gordon W. F. Drake, Tingyun Shi, Kelin Gao Precision spectroscopy of Li$^{\mathrm{+}}$ is a promising tool to test QED and measure fundamental constants. Here, we investigate the hyperfine and fine structures of 2 $^{\mathrm{3}}$S and 2 $^{\mathrm{3}}$P in $^{\mathrm{7}}$Li$^{\mathrm{+}}$ using saturated fluorescence spectroscopy based on a \textasciitilde 500 eV metastable ion beam. We measure the 2 $^{\mathrm{3}}$S$_{\mathrm{1}}\leftrightarrow $2 $^{\mathrm{3}}$P$_{\mathrm{0,1,2}}$ transitions in $^{\mathrm{7}}$Li$^{\mathrm{+}}$. The widths of \textasciitilde 50 MHz in FWHM are determined by Lamb dips, which are generated by two counter-propagating lasers perpendicular to the Li$^{\mathrm{+}}$ beam. With a triple nested loop scanning method, the long-term drift and systematic uncertainties are reduced or eliminated. The systematic uncertainties caused by the Doppler effect, line profile, laser power, frequency calibration and Zeeman effect are evaluated, giving a total uncertainty \textless 100 kHz. For the 2 $^{\mathrm{3}}$S hyperfine splittings, the accuracy is close to the previous works. For the 2 $^{\mathrm{3}}$P fine and hyperfine splittings, our values are one order of magnitude more accurate than the previous experiments and have similar accuracy to the theoretical values. [Preview Abstract] |
Thursday, June 4, 2020 12:06PM - 12:18PM |
N07.00006: Precision spectroscopy of the 2S-6P transition in atomic hydrogen Lothar Maisenbacher, Vitaly Wirthl, Arthur Matveev, Alexey Grinin, Randolf Pohl, Theodor W. H\"ansch, Thomas Udem Precision measurements of atomic hydrogen (H) have long been successfully used to extract fundamental constants and to test bound-state quantum electrodynamics. Both the Rydberg constant $R_\infty$ and the proton root mean square charge radius $r_p$ can be determined by H spectroscopy with high precision. We have previously measured the 2S-4P transition frequency to 4 parts in $10^{12}$ (A. Beyer et al., Science 358, 79 (2017)), finding good agreement in $r_p$ with the spectroscopy of muonic H (A. Antognini et al., Science 339, 417 (2013)). Recently, we have completed data-taking on the 2S-6P transition in H, which has a three times lower linewidth compared to the 2S-4P transition. This factor, together with an upgraded fluorescence detection, allows for a five-fold improvement in fractional precision. Here, we will discuss the ongoing data analysis and present preliminary results, focusing on a frequency shift from the light forces acting on the atoms. [Preview Abstract] |
Thursday, June 4, 2020 12:18PM - 12:30PM |
N07.00007: Towards a next-generation measurement of the fine structure constant Zachary Pagel, Weicheng Zhong, Andrew Neely, Eric Planz, Aini Xu, Spencer Kofford, Madeline Bernstein, Holger Mueller We present the new Berkeley experiment for measuring the fine-structure constant (alpha) as a test of the Standard model. The current leading determination of alpha reached 0.2 ppb accuracy, and is in 2.5$\sigma $ tension with the value of alpha determined from electron gyromagnetic anomaly experiments [1]. Our new experiment seeks an order of magnitude improvement in sensitivity and systematic uncertainty. By using a beam with a larger beam waist, systematic effects such as Guoy phase or effects from thermal motion of the atoms are minimized [2]. A new interferometer geometry will also be used that can cancel phase shifts from the gravity gradient and from diffraction phases [3,4]. In order to achieve high momentum transfer with a larger beam area, we will discuss progress towards a kW peak power pulsed laser system at 852nm. [1] R. H. Parker, C. Yu, W. Zhong, B. Estey, and H. Mueller, Science 360, 191 (2018). [2] C. Yu, W. Zhong, B. Estey, J. Kwan, R. H. Parker, and H. Mueller, Ann. Phys. 531, 1800346 (2019). [3] Z. Pagel, W. Zhong, R. H. Parker, C. T. Olund, N. Y. Yao, and H. Mueller, arXiv [physics.atom-Ph] (2019). [4] W. Zhong, R. H. Parker, Z. Pagel, C. Yu, and H. Mueller, arXiv [physics.atom-Ph] (2019). [Preview Abstract] |
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